In integrating laser pump cavities, the pumplight is reflected more than once. Thus, pump absorption is superimposed during several passes through the slab. In integrated laser pump cavity devices with an integral concentrator such as as described in commonly assigned co-pending patent application No. 08/994,422 [Attorney docket 970508 ], pending, the doped laser crystal and the concentrator are typically both made of the same crystal type. The doped laser crystal and the undoped concentrator are generally made using diffusion bonding technology which is well known in the industry. Diffusion bonding technology produces a bond that is as strong as the host crystal and provides a good optical, mechanical and thermal interface. Conventional diffusion bonding is performed on crystals of similar type.
Diffusion bonding of dissimilar crystal types has recently been developed by Onyx Optics under a Phase I Small Business Innovative Research (SBIR) grant, funded by the U.S. government. Specifically, a 4 mm by 4 mm interface between ytrrium aluminum garnet (YAG) and sapphire (Al.sub.2 O.sub.3) was formed by the Onyx Optics diffusion bonding process that exhibited low stress birefringence (&lt;10 nm/um wavefront retardation) without fine annealing, high bond strength (600 Mpa equivalent to bulk YAG), and high thermal shock resistance. The proposed uses to date do not include high power solid-state laser pump cavities with integral concentrators.